[0] https://slatestarcodex.com/2016/01/11/schizophrenia-no-smoki...
Nicotene is a partial substitute for Niacin (Vitamin B-3). Niacinamide sometimes helps people reduce their tobacco intake.
The first generation anti-depressants were the Mono Amine Oxidase Inhibitors (MAOIs). Tobacco has MAOI-like effects too.
I think tobacco is also an anti-estrogen... Aromatase inhibitor: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2904480/
Compulsions have to be considered in context: people get benefits from tobacco that they do actually need. My friend (a misdiagnosed 'psych patient') took up smoking when she was 12, probably because she was depressed.
Edit: submission of a CS montior link about this same news item: https://news.ycombinator.com/item?id=29500610